Microsoft 365 Inbox Forwarding Rule Created
editMicrosoft 365 Inbox Forwarding Rule Created
editIdentifies when a new Inbox forwarding rule is created in Microsoft 365. Inbox rules process messages in the Inbox based on conditions and take actions. In this case, the rules will forward the emails to a defined address. Attackers can abuse Inbox Rules to intercept and exfiltrate email data without making organization-wide configuration changes or having the corresponding privileges.
Rule type: query
Rule indices:
- filebeat-*
- logs-o365*
Severity: medium
Risk score: 47
Runs every: 5 minutes
Searches indices from: now-30m (Date Math format, see also Additional look-back time)
Maximum alerts per execution: 100
References:
- https://docs.microsoft.com/en-us/microsoft-365/security/office-365-security/responding-to-a-compromised-email-account?view=o365-worldwide
- https://docs.microsoft.com/en-us/powershell/module/exchange/new-inboxrule?view=exchange-ps
- https://docs.microsoft.com/en-us/microsoft-365/security/office-365-security/detect-and-remediate-outlook-rules-forms-attack?view=o365-worldwide
- https://raw.githubusercontent.com/PwC-IR/Business-Email-Compromise-Guide/main/Extractor%20Cheat%20Sheet.pdf
Tags:
- Elastic
- Cloud
- Microsoft 365
- Continuous Monitoring
- SecOps
- Configuration Audit
Version: 3 (version history)
Added (Elastic Stack release): 7.13.0
Last modified (Elastic Stack release): 8.2.0
Rule authors: Elastic, Gary Blackwell, Austin Songer
Rule license: Elastic License v2
Potential false positives
editUsers and Administrators can create inbox rules for legitimate purposes. Verify if it complies with the company policy and done with the user’s consent. Exceptions can be added to this rule to filter expected behavior.
Investigation guide
edit## Config The Office 365 Logs Fleet integration, Filebeat module, or similarly structured data is required to be compatible with this rule.
Rule query
editevent.dataset:o365.audit and event.provider:Exchange and event.category:web and event.action:"New-InboxRule" and ( o365audit.Parameters.ForwardTo:* or o365audit.Parameters.ForwardAsAttachmentTo:* or o365audit.Parameters.RedirectTo:* ) and event.outcome:success
Threat mapping
editFramework: MITRE ATT&CKTM
-
Tactic:
- Name: Collection
- ID: TA0009
- Reference URL: https://attack.mitre.org/tactics/TA0009/
-
Technique:
- Name: Email Collection
- ID: T1114
- Reference URL: https://attack.mitre.org/techniques/T1114/
Rule version history
edit- Version 3 (8.2.0 release)
-
- Formatting only
- Version 2 (8.1.0 release)
-
- Rule name changed from: Microsoft 365 New Inbox Rule Created
-
Updated query, changed from:
event.dataset:o365.audit and event.provider:Exchange and event.category:web and event.action:"New-InboxRule" and event.outcome:success